(1) Field of the Invention
The present invention relates to medical devices and more particularly to medical devices for noninvasive diagnostic measurement of the human body.
(2) Brief Description of the Prior Art
Various devices are known for providing noninvasive diagnostic measurements on the human body.
U.S. Pat. No. 4,295,471 to Kaspari, for example, discloses an apparatus for noninvasively monitoring arterial waveforms, such as the waveform produced by blood flow through the brachial artery in a human subject. The apparatus includes a transducer which senses both a pressure wave proportional to blood flow in the artery and an acoustical signal through a partially occluded artery.
U.S. Pat. No. 4,437,468 to Sorenson et al. discloses an ultrasound scanning system particularly adapted for scanning large body areas such as the back. There is a plurality of ultrasound transducers, each mounted in a transducer shoe, and each shoe in turn mounted on a plunger which seats in the bore of a housing so that it is free to move independently from the other transducers in a direction parallel to the bore, but is constrained to move with the other transducers in the two perpendicular directions. A spring seated in the bore between the housing and the plunger provides a bias force to maintain a positive and uniform contact between the transducer and the back.
U.S. Pat. No. 4,580,574 to Gavish discloses an ultrasound device for continuously and noninvasively monitoring instantaneous fluctuations in viscoelastic-related properties of tissue comprising a pair of substantially parallel spaced-apart piezoelectric transducers having a gap therebetween and adapted to bracket and come in direct contact with living tissue inserted in the gap between the transducers, at least one of the transducers being adjustable with respect to the other transducer whereby the distance between the transducers is adjustable to enable insertion and clamping of a segment of living tissue therein.
U.S. Pat. No. 4,836,212 to Schmitt et al. discloses a measuring apparatus for the noninvasive determination of peripheral outflow and flow disturbances in the extremities of human beings includes at least one light transmitter for directing light onto the skin of the subject under test and at least one light receiver for receiving reflected radiation and an evaluation and read-out circuit for ascertaining the temporal course of the blood outflow or inflow in the veins by measuring the changes in light reflection.
U.S. Pat. No. 5,360,005 to Wilk discloses a medical diagnostic method that comprises the steps of automatically sensing an acoustic vibration to an electrical signal, and converting the amplified electrical signal to an acoustic pressure wave. The steps of sensing and converting the sensed acoustic vibration to an electrical signal are implemented by operating an acoustoelectric transducer in a hand held device, and the method further comprises the step of holding the hand held device against a skin surface of the person.
U.S. Pat. No. 5,365,937 to Reeves et al. discloses a sensing device for capturing acoustic heart sounds. The sensing device has a diaphragm formed from a piezoelectric transducer material that generates excitation signals in response to acoustic and vibratory energy outputs. The sensing device includes metallization layers on the diaphragm for receiving and transmitting the excitation signals to an output display device via associated electrical contacts and electrical leads and also includes a layer of adhesive material for coupling the sensing device to the subject.
In taking noninvasive measurements of the human body, it is also know that array based measurements are ideal for situations where the signal-to noise ratio is small, such as energy emissions in the human chest. It is also found, however, that the ribs can physically block these emissions or alter them by causing scattering of the wave (energy) field.